Electrical test prod



Jan. 1, 1952 v R KRAFT HAL 2,580,682

ELECTRICAL TEST PROD Filed Nov. 15, 1949 RUSSELL E. KRAFT GEORGE WASHINGTON JR.

INVENTORS ATTORNEY Patented Jan. 1, 1952 ELECTRICAL TEST'PROD 7 Russell E; Kraft, Parsipany, and George Washington, Jr., Morristown, N. .L, assignors to United Technical Laboratories, Morristown,

N. J a partnership Application Novembe1215, 1949, Serial No. 127,402 2 Claims. (01. 173-273) This invention relates to electrical contacting devices and more particularly to an electrical. test prod of the type employed to make electrical tests ormeasurements in confined'spaces;

A 'test prod is a necessary tool in the-artof testing radio, television and other electronic equipment. Such equipment comprises a maze of components, wires and other electrical conducting members assembled in a chassis'having the smallest practicable overall dimensions. A test prod is particularly adapted for use in establishing contact with electrical wires or terminal members which are closely adjacent to other wires or terminals or which are located in the innermost sections of thechassis.

An ideal test prod shouldinclude the following features:

1. Quick, easy and positive establishment of electrical contact with a minimum possibility of causing short circuits.

2. Adapted to penetrate overlying insulation, for establishment of contact with normally insulated wire.

3. Adapted for easy and positive. attachment to a wire thus leaving the hands of: the user free for other purposes.

4. Adapted for insertion into conventional-pinjacks and vacuum tube sockets.

5. Designed for solderless connection of the a test prod of simple construction and maximum facility of use.

An object of this invention is the provision of a test prod in which the lead wire may-be attached to the prod tip without recourse to a soldered joint.

An object of this invention is the provision of a test prod provided with a contact tip adapted for insertion into conventional pin-jacks and for establishing a holding contact on a bare wire, soldering lug, etc.

An object of this invention is the provision of a test prod comprising a handle ofinsulating material, a contact tip extending from one end of the handle, a longitudinal groove in said tip, a

springwire disposed within the said longitudinal groove and extending beyond the end ofthe contact tip and transverse notches extendingacross the longitudinal groove.

These and other objects and advantages will become more apparent mm. the following description taken in connection with the accompanying drawings. The drawings are for purposes of illustration and are not to be construed as definingthescope or limits of the invention which resides inthecombination and arrangement-of parts as set forth in the appended claims.-

In the drawings wherein like characters refer to like parts in the several views:

Figure 1 is an isometric view of the metallic contact member employed-to make a test prod in. accordance with this invention;

Figure 2 shows the spring wireadapted to lie in the longitudinal groove'of the contact member;

Figure 3 illustrates theassembledcontact' tip;

Figure 4 illustrates atest lead having a test prod on each end;

Figure 5 is an enlarged, cross-sectional view of a complete test prod andshowing the solderless joint between the end of the lead wire and the contact tip; and

Figures 6 and 7 illustrate how the test prod may be attached to awire to free the hands of theuser :for other purposes. I Referring now to Figures 1-3, the contact tip of the test prod comprises a metallic member it having an inner end H of somewhat reduced diameter ahd threaded, as shown. The threaded end ll includes an axial channel E2 of varying depth, the depth of the channel being a maximum at the free end of the threaded section. The outer end ofthe member H] comprises an integral,, elongated rod I3 of reduced diameter. A longitudinal groove 14 extends throughout the entire length of the rod 'l3'and partially through the member It, and'the resulting side walls of the'rod are provided with transverse notches l5, substantially as shown.

The pointed wire I6 is made of good spring steel and is disposed within the longitudinal groove 24, said wire being secured into place by peaning over the adjacent side walls of the member It as indicated by the numeral l'l. It is pointed out that the dimensions of the longitudinal groove' l4 and the wire l6 are such that when the wire is in place (Figure 3), it lies completely within the effective, outside diameter of the rod !3. Thus, the presence of the wire is will not in any way interfere with the insertion of the rod l3 into a pin-jack connector, the prongs of a vacuum tube socket, or etc., it being noted that the free end of the rod I3 is'slightly rounded for this purpose.

The assembled contact tip, as shown in Figure 3, is threaded into an appropriatetubular shell to form a test prod. Figures illustrates-a cable orlead wire 20 having a test prod on each end. The shell 2| is relatively long as such prod is intended primarily for use in establishing an electrical test connection, with a wire, while the shell 22 is relatively short and better adapted for a test prod designed for insertion into a pinjack or vacuum tube socket. In either case the contact tips are identical and it will be apparent various combinations of long or short prods is possible as well as single prods in which case the other end of the cable can be connected to an instrument binding post.

While it will be obvious that the end of the lead wire 20 can be soldered within the channel I! of the contact member, we prefer to make a firm connection between the cable and the tip without the use of a soldered joint. The solderless connection is shown-in Figure 5 which is a longitudinal cross-sectional view of the short test prod illustrated in Figure 4. The shell 22 which is made of plastic or other electrical insulating material is provided with a bore 25 having a diameter slightly greater than the outside diameter of the member l0, and a threaded section 26 corresponding to the threaded end ll of the said contact member. Inasmuch as the threaded section 26 is of a smaller diameter than the bore 25 there is provided a shoulder 21 within the shell 22. In assembling the test prod the insulation is removed from the end of the lead wire 20 and this end of the wire is passed through theshell 22. The bare end of the wire is placed into the channel l2 in the contact tip with the end of the wire projecting slightly over the mem her In. The contact member is then threaded into the shell until the end of the lead wire is clamped firmly between the member l and the shoulder 21' of the shell, as shown in Figure 5.-

change at will the size or lengthof the asso ciated lead wire.

Figures 6 and 7 illustrate the manner of attachingour test prod to abare wire in order to free the hands of the user for other purposes.

The projecting end of the spring wire I6 is placed,

into contact with the wire 30 and a slight downward pressure is exerted upon the test prod as a whole. shown in Figure 6, to a point where the, wire .30 can be grasped between the rod. l 3 and the sprin wire I6. An axial movement ofthe shell 2| will now cause-the wire 30 to slip into thetransverse notches l after which the hand may be removed from the test. prod, the latter being held in firm contact with the wire 30- by reason of the tension exerted thereon by thespring wire 16. To remove the test prod a reverse procedure is followed.

Having now described our invention the universal adaptability of the test prod is apparent. Any portion of the rod l3, may be used to estab lish electrical contact with; an uninsu-lated wire or circuitcomponent. Alternatively, the:pointed end of the springwire. l6 ,may be emplo'yed to puncture through insulation, films of oil or grease, or to penetrate into metal to prevent accidental slippage of the prod as a whole. The attachment of the test prod to a wire in order to free the hands of the user can be .done quickly and conveniently. In addition the prod may be employed as the plug-in element of a pin-jack arrangement as the rod leis of uniform diameter throughout its length. I V

This causes the wire IE to flex,'as

While we have described and illustrated a preferred embodiment of our invention it will be apparent the handle portion of the device need not be a tubular shell. The lead wire can be soldered to the metallic contact tip and a suitable plastic or rubber handle molded around such combination.

Other modifications in the form, shape and arrangement of the parts will be apparent to those skilled in the art. Such modifications can be made without departing from the scope and .spirit of the invention as set forth in the following claims.

We claim:

1. A metallic contact member for a test prod comprising a unitary, cylindrical body having a thread on one end and the other end being a cylinder of reduced diameter forming a tip section; a slot in the threaded end of the body; a longitudinal groove extending the full length of the tip section and partially into the body; a pair of transverse alined notches in the opposed side walls formed by the groove of the tip section; and a spring wire having one end disposed within the groove in the body and secured to said body, a central portion disposed within the groove in the tip section, and a pointed end extending beyond the said tip section, said wire having a diameter substantially equal to the radial depth of the groove in the tip section.

2. An electrical test prod comprising a tubular shell of insulating material having an internallythreaded section proximate to one end; an enlarged-diameter bore in one end of the shell said bore communicating with the internally-threaded section; a unitary metallic member having an externally-threaded inner end that is threaded into the threaded section of the shell, a central section-disposedwithin'the said bore, and a uniform, reduced-diameter tip section extending outwardly of the shell; a radial slot in the threaded 'end' of the metallic member, a lead wire extending from the other end ofthe shell said lead wire having an end disposed within the radial 'slot' in -the threaded end of the metallic member and clamped between the central section of the metallic member and the bottom wall of the said enlarged-diameter bore; a longitudinal im r groove extending the full length of the said tip section and partially into'the'central section of the metallic member; a pair of transverse, alined notchesin'the opposed side walls-formed by the groove of the tip section; and a spring wire having an end'secured to the central section of the metallic member and a pointed end extending beyond the said tip section, said wire having a central'portion disposed within the groove in the tip section and the diameter -of the wirebeing substantially equal to the radial depth of the groove in the said tip section.

RUSSELL E. KRAFT. GEORGE WASHINGTON, JR..

REFERENCES CITED uThe following'references are of record in the file of this patent:

' l UNITED'S'IATES PATENTS Name. Date 111,093 Coughlin Sept. 17, 1889 9,4 4,271, Morrell Dec. 28, 1909 1,324,177 Sherman Dec. 9, 1919 2,438,350, Reichard Mar. 23, 1948 'Novel1o Aug. 2, 1949 

